Barcodes may be applied to various products in different ways. Conventional barcodes may be attached to products using pre-printed barcode labels or may be printed directly onto the product itself. Other ways of applying barcodes to products may include a technique known as direct part marking (DPM), which is a process of permanently marking objects with barcodes or other information. The DPM process may include creating one-dimensional symbols (e.g., Code 39 codes, Code 128 codes, etc.) or two-dimensional symbols (e.g., Data Matrix codes, quick response (QR) codes, etc.). The DPM process may include marking the objects using various marking techniques, such as by engraving, laser marking, embossing, abrasive blasting, molding, electrochemical etching, or other techniques.
Since the various types of DPM barcodes may be applied using different techniques and may be applied to different surfaces, typical DPM barcode readers require multiple illumination systems to read the DPM barcodes. The illumination systems usually contain at least two assemblies, a first assembly including a dark field illumination system that provides low angle incident lighting on the barcode substrate. Dark field illumination is usually needed for reading barcodes that are embossed on a highly reflective substrate. A second assembly of the illumination systems may include a bright field illumination system, which provides high angle incident lighting on the substrate. Bright field illumination is usually needed for reading barcodes engraved on a diffused or non-polished metal surface. An optional third assembly may include light-diffusing illumination components, which may be used to assist in reading a barcode engraved on a curved surface.
The multiple illumination system assemblies for assisting the DPM barcode readers can therefore be complex to assemble, bulky, and expensive. Also, these illumination systems can consume a high amount of power, particularly because of the high number of light emitting diodes (LEDs) that are needed for proper illumination. Therefore, a need exists for a simpler, less expensive, and more energy efficient illumination system that may be used for DPM barcode readers.